If, after opening a hydrant, the engine suction gauge drops below the safe operating range, which steps should be taken?

If, after opening a hydrant, the engine suction gauge drops below the safe operating range, which steps should be taken?

• A. Check for suction leaks or closed valves, ensure hydrant is delivering water, re-prime, and adjust or reposition as needed
• B. Increase throttle to maximum
• C. Disconnect the hydrant and recalibrate the gauge
• D. Ignore the gauge and continue operations

Answer: (D)

The main idea here is that a drop in the engine suction gauge means the pump is losing prime on the suction side and cannot develop the required vacuum to draw water. The proper response is to systematically identify and fix suction problems and then re-prime the pump so water is actually being drawn. Start by inspecting the suction side: look for leaks in hoses, fittings, and couplings, and verify that no valves on the suction side are accidentally closed. Make sure the hydrant is delivering water by confirming the hydrant valve is fully open and that water is reaching the pump intake. If air is entering the line, this is what’s causing the low reading. Re-prime the pump as needed. This typically involves filling the pump and suction line with water and removing any air pockets until the suction gauge shows a stable, proper vacuum. If necessary, adjust or reposition the suction setup—tighten connections, correct hose routing, or move to a lower elevation or shorter distance to the water source to improve prime. Increasing throttle to maximum won’t fix suction problems and can risk cavitation or damage. Disconnecting the hydrant and recalibrating the gauge does not address the real issue of water supply and prime. Ignoring the gauge is unsafe and could lead to pump damage or loss of water supply.

The main idea here is that a drop in the engine suction gauge means the pump is losing prime on the suction side and cannot develop the required vacuum to draw water. The proper response is to systematically identify and fix suction problems and then re-prime the pump so water is actually being drawn.

Start by inspecting the suction side: look for leaks in hoses, fittings, and couplings, and verify that no valves on the suction side are accidentally closed. Make sure the hydrant is delivering water by confirming the hydrant valve is fully open and that water is reaching the pump intake. If air is entering the line, this is what’s causing the low reading.

Re-prime the pump as needed. This typically involves filling the pump and suction line with water and removing any air pockets until the suction gauge shows a stable, proper vacuum. If necessary, adjust or reposition the suction setup—tighten connections, correct hose routing, or move to a lower elevation or shorter distance to the water source to improve prime.

Increasing throttle to maximum won’t fix suction problems and can risk cavitation or damage. Disconnecting the hydrant and recalibrating the gauge does not address the real issue of water supply and prime. Ignoring the gauge is unsafe and could lead to pump damage or loss of water supply.